This invention pertains to a thin-film, floppy and compliant, electromagnetic read/write head array structure. More particularly, it pertains to such a structure which is intended to be used in compliant, pressure-biased contact with a magnetic imaging medium, with little appreciable medium wear occuring as a consequence of such contact.
A recently emerging magnetographic technology, born from the inventions disclosed in my prior-filed U.S. application which are identified as follows:
MAGNETIC IMAGING METHOD AND APPARATUS, Ser. No. 170,788, Filed 7/21/80 now U.S. Pat. No. 4,414,554; PA1 MULTIPLE HEAD MAGNETIC RECORDING ARRAY, Ser. No. 381,923, Filed 5/26/82; PA1 DIFFERENTIAL-PERMEABILITY FIELD-CONCENTRATING MAGNETIC WRITING HEAD, Ser. No. 381,922, Filed 5/26/82 (now abandoned);
has made possible high-resolution, high-quality, low-cost magnetic imaging. Disclosed in those applications are several different types of thin-film imaging heads, and an array of such heads, which may be used to create and read an endless variety of images, such as lettrs in the alphabet.
One of the important features which is offered by the thin-film structures disclosed in these three prior applications, is that the main supporting substrate in each structure takes the form of a glassy amorphous material known under the trade designation "Metgals". See, particularly, application Ser. No. 170,788, filed 7/21/80, entitled MAGNETIC IMAGING METHOD AND APPARATUS for a more detailed identification of this material. Among other important contributions made by Metglas in the head structures disclosed is that it is an extremely hard material which permits it, with extremely low-wear consequences (regarding a magnetic imaging medium), to be pressure-biased into contact with such a medium for the closest possible magnetic coupling during reading/writing operations. In addition, its flexibility allows a head organization constructed in accordance with those applications to comply easily with curvilinearity in a confronting medium.
While such compliant low-gear contact is strikingly offered by the structures disclosed in the above-referred-to three applications, because of the way in which the individual read/write heads are formed (somewhat like spaced islands or projections) on the face of a Metglas substrate, pressure-biasing during a read/write operation results in some point-pressure telegraphing through the substrate to a contacting medium. Thus, while low-wear performance is clearly offered, it is not as maximized as it could be in the absence of such point-pressure telegraphing.
A general object of the present invention therefore, is to provide, with respect to electromagnetic, thin-film, read/write head structures like those disclosed in the above-identified applications, additional structures which tends to "planarize" (fill-in topography) of that side of the Metglas substrate which bears the projecting head structure, thus to reduce appreciably and likelihood of point-pressure telegraphing like that just outlined.
A related object is to provide such an organization wherein a portion of the additional "planarizing" structure just mentioned is formed using part of the conductive highway system which connects with coils in the read/write head structures.
While the resulting structure, on the side of the substrate where the head coils are formed, has obvious non-planar topography, care is taken, according to the invention, to place the additional fill-in "planarizing" structure in such a manner that normally applied forces, spreading, as is customary, outwardlyt as they transmit through the substrate, converge vectorially no further than the opposite face of the substrate, thus to avoid any significant preferential pressure points.
According to a preferred embodiment of the invention, the proposed head array structure includes a thin-film, floppy and compliant web, or substrate, of the type mentioned above. Individual read/write heads, and associated energizing conductive structure, are distributed like "bumps" on one face of the substrate--the opposite face of which is designed to contact a magnetic imaging medium during a read/write operation. Other "bumps", some of which are formed over the connecting conductive structure for the heads, and others which are isolated like islands from the heads, are distributed over the first-mentioned substrate face in a manner whereby they cooperate with the head bumps to minimize point-pressure telegraphing in the kind of operational situations mentioned above.
Various other objects and advantages are attained by the invention, and these will become apparent as the description which now follows is read in conjunction with the accompanying drawings.